This would be an ICC conversion rather than any proprietary method, would that be correct. If it's using an ICC conversion, than a cmyk->cmyk++ conversion is intending to match the original CieLab values of the raster image, which wouldn't necessarily take advantage of the larger gamut. As such I would fail to see any true advantage for cmyk imagery. I also understood that raster conversions were handles by the Prinergy workflow rather than Spotless itself?
We don't sell or support Spotless, one of our proofing customers just happens to use it, so I don't have any training or deep product knowledge. I am learning as I go!
The Prinergy refine process uses A CMYK++/+ profile for refining incoming CMYK+ files (I don't recall if it is an ICC or DeviceLink).
All the conversion is attempting to do is reproduce the original colour as close as possible, using the different ink set used by the Spotless implementation. So if an original used CMYK+485, then the conversion to CMYKOG or whatever inks were being used would attempt to reproduce the input colour as closely as possible (the red may use MYO, where as the original used only 485). If the source image was only CMYK and the destination ink set used CMYK, then I believe that there would be no addition of spot inks into the images.
AFAIK it is not about expanding the gamut - it is about matching/coming close to the original colour using different "standard" inks. If the larger gamut is in the source file and it is possible to be reproduced in the destination file, then the larger gamut will be retained.
The raster and vector conversions both appear to be handled by the Prinergy workflow. From what I understand, the CMYK+++ colour profile is created as part of the Spotless setup/implementation for the chosen ink set. I misunderstood how deeply Spotless was tied into Prinergy (it is not directly tied in at all from what I now gather). ColorFlow is a separate program, however it is tied into Prinergy, I mistakenly believed that Spotless was similar in it's behaviour.
I am presuming that the Prinergy CMYK+++ profile delivers the same CMYK+++ colour build to vector and raster elements as what the original Spotless recipe called for, however the build may be different - as long as the end colour is the same.
With luck Gordo can clarify.
Stephen Marsh